package thread;

// 通过懒汉模式实现单例模式
class SingletonLazy {
    volatile private static SingletonLazy instance = null;

    public static SingletonLazy getInstance() {
        // 这个条件，判断是否要加锁，如果对象已经有了，就不必加锁了，
        if (instance == null) {
            synchronized (SingletonLazy.class) {
                if (instance == null) {
                    instance = new SingletonLazy();
                }
            }
        }
            return instance;
        }
    private SingletonLazy() {}
    }

    public class Demo14 {
        public static void main(String[] args) {
            SingletonLazy s1 = SingletonLazy.getInstance();
            SingletonLazy s2 = SingletonLazy.getInstance();
            System.out.println(s1 == s2);
        }
    }
